In general, a semiconductor wafer is subjected to surface planarization using a chemical-mechanical polishing apparatus.
The chemical-mechanical polishing apparatus is an apparatus for polishing an oxide film or a thin metal film applied on a semiconductor wafer using a chemical action and a physical action, thereby planarizing or removing the oxide film or the thin metal film.
As illustrated in FIG. 1, the chemical-mechanical polishing apparatus includes a rotatable polishing head 5, a polishing pad 6, and an abrasive-supplying part. The polishing head 5 is connected to a motor, and has a wafer-accommodating portion in the bottom thereof, the wafer-accommodating portion accommodating a semiconductor wafer 7 therein. The polishing pad 6 is disposed on the bottom of the polishing head 5 polishes the surface of the semiconductor wafer 7 accommodated in the polishing head 5. The abrasive-supplying part supplies a chemical abrasive to the polishing pad 6.
In addition, a retainer ring 1 defining the wafer-accommodating portion is mounted to the lower portion of the polishing head 5.
The retainer ring 1 includes a first ring body 1a mounted on the carrier of the polishing head 5 and a second ring body 1b coupled to the lower portion of the first ring body 1a. The second ring body 1b has a plurality abrasive supply holes in the bottom surface, and adjoins the abrasive pad 6.
The first ring body 1a and the second ring body 1b are coupled and integrated by bonding using an adhesive.
The first ring body 1a is formed of a metal material, such as stainless steel (SUS), and the second ring body 1g is formed of an engineering plastic.
The retainer ring 1 is fabricated according to a variety of specifications according to the type of chemical-mechanical polishing apparatus to which the retainer ring 1 is mounted, and is fabricated according to the specifications of the corresponding chemical-mechanical polishing apparatus.
That is, during the chemical-mechanical polishing operation performed within the wafer-accommodating portion of the polishing head 5, the outer circumferential surface of the semiconductor wafer 7 is caught by the inner circumferential surface of the retainer ring 1 such that the semiconductor wafer 7 is not dislodged from the polishing head 5.
In addition, the chemical abrasive slurry supplied to the polishing pad by the abrasive-supplying part enters the semiconductor wafer-accommodating portion through the abrasive supply holes to oxidize the surface of the semiconductor wafer.
The chemical-mechanical polishing apparatus planarizes the surface of the semiconductor wafer by repeatedly performing a chemical oxidation operation using the slurry and a polishing operation. In the polishing operation, the polishing head and the polishing pad rotate to polish the surface of the semiconductor wafer in contact with the polishing pad.
At present, for chemical-mechanical polishing apparatuses, required is a retainer ring that can be reliably and firmly mounted on the polishing head 5. The weight or height of the retainer ring needs to be preset to minimize vibration due to the contact with the polishing pad.
The retainer ring 1 is fabricated by increasing the thickness of the first ring body 1a formed of a metal material in order to obtain the specifications, such as the preset weight and height.
However, the retainer ring 1 is mounted on the polishing head 5 such that only the first ring body 1a formed of a metal material is fastened with bolts. This decreases the bonding force of the portions to which the second ring body 1a is bonded, thereby failing to reliably support the semiconductor wafer 7. Thus, scratches may be formed on the surface of the semiconductor wafer 7, and in severe cases, accidents in which the semiconductor wafer 7 is broken during the chemical-mechanical polishing operation may frequently occur.
In addition, the retainer ring 1 fabricated by bonding the first ring body 1a and the second ring body 1b is subjected to the following problems: While the retainer ring 1 is being polished, a bonding material may frequently leak to the outer circumference. The leaked bonding material frequently forms scratches on the surface of the semiconductor wafer 7 while the cured bonding material is being detached.